In our screening program for antihypertensive plant constituents extracts of the leaves and bark of Badula barthesia showed strong in vitro inhibition of angiotensin converting enzyme (ACE). Rapanone (1), 2,5-dihydroxy-3-tridecyl-1,4-benzoquinone, was isolated as an active constituent of the leaves.
The first synthesis of the unusual nitrogen-containing 3-alkyl-1,4-benzoquinone, N-(3-carboxylpropyl)-5-amino-2-hydroxy-3-tridecyl-1,4-benzoquinone, isolated from Embelia ribes, is reported. The key steps are a microwave-assisted combined Mitsunobu reaction-Claisen rearrangement to introduce the